Supermicron-size aerosol particles originating from biomass burning in south-central Africa

Atmospheric Science;Biomass Burning;Aerosol;Microphysics;Africa;ORACLES;Superaggregate

Miller, Rose Marie ; McFarquhar, Greg M ; Rauber ; Robert M

关键词: Atmospheric Science;    Biomass Burning;    Aerosol;    Microphysics;    Africa;    ORACLES;    Superaggregate;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/105697/MILLER-THESIS-2019.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

During the 2017 & 2018 Observations of Aerosols Above Clouds and their Interactions (ORACLES) field campaign, the NASA P3-Orion was equipped with a 2D-Stereo (2D-S) probe that contains 128 diodes that are 10 µm in size nominally measuring particles with sizes ranging from 5 µm < D < 1280 µm. The 2D-S probe captured suspended supermicron-sized aerosol particles (SAPs) within a biomass burning (BB) plume duringresearch flights over the South East Atlantic Ocean outside of clouds at times when no liquid water was detected by the King liquid water probe. Numerous SAPs sized between 10 µm and 1.52 mm were observed at altitudes ranging from 1230 m to 3500 m mostly between 7-11°S along 5°E, 1000 km from the coastline. Concentrations (500-1200 cm-3) of refractory black carbon (rBC) measured by a single particle soot photometer at the same time suggest these SAPs are composed of rBC, also referred to as soot. Transmission electron microscopy (TEM) images of submicron particulates were collected on TEM Holey carbon grid filters concurrently with the probes. These TEM images reveal particles with crystalline structures as well as carbonaceous particles. Energy-dispersive X-ray spectroscopy (EDS) spectra from the filters revealed elevated levels of potassium (K) and oxygen (O) indicating the particles are of biomass burning origin. NOAA HYSPLIT (Hybrid Single Particle Lagrangian Integrated Trajectory) models for three-day back trajectories show a source location in northern Angola for the time periods when large SAPs were observed. FIRMS (Fire Information for Resource Management System) MODIS 6 (Moderate Resolution Imaging Spectroradiometer) active fire maps showed extensive biomass burning at these source locations. Given the source location, the high concentrations of rBC, and the TEM-identified carbonaceous particles, it is hypothesized that the SAPs imaged by the 2D-S are examples of large soot superaggregates or unburned plant material previously seen in biomass burning smoke. The SAPs, if they are composed of rBC could have a role on the radiative budget of the region where they were observed.